The present invention relates to a navigation method and system for a vehicle, and more particularly, to a navigation method and system for stable and prompt vehicle guidance when the vehicle passes a crossroad.
A recent navigation system for a vehicle stores a digital map in a data storage unit, determines the vehicle position on the digital map, and guides the driver along an optimal route. To guide the vehicle on the route, the navigation system, having calculated a target route to a target place as the optimal route, also indicates an appropriate direction to take when the vehicle approaches a crossroad.
If the vehicle does not follow the target route, but instead proceeds on a different branch of the crossroad, the navigation system has to calculate a new target route based on the branch the vehicle is traveling. However, there are problems with guiding the vehicle in the prior art. For example, if two crossroads are near each other, when a vehicle takes a branch departing from the target route at the first crossroad, a new target route must be calculated before the vehicle arrives at the second crossroad. But the time required to calculate the new target route is not negligibly small, and sometimes it is only after the vehicle arrives at the second crossroad that the calculation of the new target route is completed.
Thus, the vehicle position after the second crossroad does not correspond to the new target route and a new calculation of a new target route must be executed. Therefore, the navigation system does not perform the vehicle route guiding function for a substantially long period.
The information disclosed in this Background of the Invention section is only for enhancement of understanding of the background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art that is already known to a person skilled in the art.
A preferred embodiment of a navigation method for guiding a vehicle on a route includes: calculating a target route for guiding the vehicle; detecting a forthcoming crossroad on the target route; displaying a signal for informing of the forthcoming crossroad; determining if a relevant turn signal, corresponding to the target route at the crossroad, is operated before the vehicle arrives at the crossroad; calculating at least one backup route different from the target route at the crossroad, when the relevant turn signal is not operated; determining a current vehicle position after the crossroad; determining if the current vehicle position after the crossroad lies on the target route; and changing the target route when the current vehicle position after the crossroad does not lie on the target route.
It is preferable that the changing of the target route changes the target route to one of backup routes. More preferably, calculating the backup routes calculates backup routes for each branch from the crossroad, and changing the target route changes the target route to a backup route on which the vehicle is positioned after the crossroad.
It is also preferable that determining if a relevant turn signal, corresponding to the target route at the crossroad, is operated is executed when a distance between the vehicle and the crossroad falls within a predetermined distance range. It is also preferable that determining if a relevant turn signal, corresponding to the target route at the crossroad, is operated is executed when an expected time for the vehicle to arrive at the crossroad falls within a predetermined time range.
A navigation system for guiding a vehicle on a route according to a preferred embodiment of the present invention includes a data storage unit for storing digital map data, a display unit for displaying received signals, an electronic control unit, and a turn signal operation detector.
The electronic control unit preferably executes instructions for calculating a target route for guiding the vehicle; detecting a forthcoming crossroad on the target route; displaying a signal for informing of the forthcoming crossroad; determining if a relevant turn signal, corresponding to the target route at the crossroad, is operated before the vehicle arrives at the crossroad; calculating at least one backup route, different from the target route at the crossroad, when the relevant turn signal is not operated; determining a current vehicle position after the crossroad; determining if the current vehicle position after the crossroad lies on the target route; and changing the target route when the current vehicle position after the crossroad does not lie on the target route.
It is also preferable that the exemplary navigation system further includes a GPS signal receiver for receiving GPS signals from a GPS satellite, and accordingly said determining a current vehicle position after the crossroad determines the current vehicle position on a digital map, based on received GPS signals. In a preferred embodiment, the navigation method for guiding a vehicle includes; detecting a current vehicle position; calculating a target route for the vehicle; detecting an approaching crossroad along the target route; displaying a signal informing of the approaching crossroad; determining if a turn signal indicates that the vehicle will follow the target route; calculating a backup route if the turn signal indicates that the vehicle will not follow the target route; determining a post-crossroad current vehicle position after the vehicle has passed the crossroad; determining if the post-crossroad current vehicle position lies on the target route; and changing the target route to the backup route if the post-crossroad current vehicle position does not lie on the target route. Preferably, the method calculates a backup route for each branch of the approaching crossroad.
In an additional embodiment, the method also includes detecting a crossroad on the backup route; and calculating a second backup route corresponding to the crossroad on the backup route.